Operating and speed control mechanisms for revolving doors have become quite highly developed and sophisticated in the prior art as evidenced by U.S. Pat. Nos. 3,307,660; 3,717,954 and others.
It has consistently been the objective in the prior art to compress these revolving door speed control mechanisms into ever more compact packages, particularly in the vertical dimension in the interest of providing a very low profile for mounting in ceilings. Present day architects are specifying extremely shallow sight lines which require the entire mechanism to be housed within a three inch thick ceiling. In the case of the present invention, the manually operated version is only l3/4 inch thick overall, while the motor-operated embodiment is well under three inches, constituting a marked improvement over the prior art. Similarly impressive dimensional reductions have also been attained in the horizontal plane due to the employment of a more compact gear train and associated elements.
In the present invention, a far greater gear speed reduction between motor shaft and door shaft is attained by the use of fewer gears in a more compact configuration and by means of a cantilevered mounting of a high speed motor-driven pinion relative to an intermediate Evoloid gear having a concave or umbrella-like construction. As a result of this very compact and efficient gearing, certain unexpected benefits for the mechanism have been obtained without addition of parts or other complexities. Among these benefits are an improved flow of lubricant to the friction brake surfaces of the mechanism, apparently due in part to the small diameter of the high speed drive pinion along which the oil may climb toward the centrifugal brake unit and then toward the top cover plate of the mechanism. Because of this improved circulation of lubricant, no auxiliary lubricant pumping means may be employed in the mechanism. Additionally and unexpectedly, an increased degree of braking force has been obtained from the same size brake unit previously employed with lesser braking effect. This is thought to be at least in part the result of decreasing efficiency of the very high speed and high ratio gear train as the load thereon increases and its speed and efficiency decreases gradually. This appears to result in a much greater braking force at the output shaft than could normally be expected from the action of the friction brake shoes alone.
Another great advantage of the invention resides in the employment of a unique magnetic flux permeable cover plate which, in addition to lending structural support to the mechanism at key points, provides a return flux path for the permanent magnet motor which allows elimination of the lower half of the motor with a resulting further reduction in the vertical profile or height of the mechanism.
While the above are among the primary improvement features present in the invention, quite a number of additional important features are also present, only a few of which will now be mentioned.
In terms of the overall structure or mechanism, the following additional features of improvement over the prior art have been obtained:
1. Lower cost both of material purchased and of manufacturing.
2. Higher gear ratio and smallest motor drive known for revolving doors.
3. Mechanism is adaptable to all existing doors either as an overhead drive or floor-mounted, with or without door wing roll aside feature.
4. Lowest known power consumption on any revolving door system.
5. Entire mechanical and electrical system may be mounted in space between ceiling joists for easy adjustment and maintenance.
6. A simplified timing arrangement requires minimum knowledge by field installors or mechanics.
7. Umbrella-shaped intermediate gear in combination with cantilevered high speed pinion allows shallowest manual unit ever produced, allowing architects to specify thinnest sight line with speed control mounted in ceiling, rather than the less desirable floor mounting, where water and dirty environment dictate much more maintenance.
8. More efficient lubricating system allows fuller lubrication with less oil, thereby reducing torque drag caused by oil pumping.
The improved unit cover plate embodies the following features or functions:
1. Serves as a bearing retainer for all shafts which is unique in a revolving door speed control or motor drive.
2. Seals mechanism against oil leaks, water leaks and dirt contamination.
3. Forms a compressive support to carry the load of the door as transmitted through widely spaced dowel pins.
4. Allows eliminating lower half of pancake motor by serving as a return path for magnetic flux during motor operation, and provides an efficient heat sink for the motor.
5. Forms a mounting means for adjustable door timing mechanism and associated reed switch and a mounting means for the door centershaft seal.
The improved gear housing or casting possesses the following features:
1. Smaller size makes possible the adoption of smaller cornices for manual and motor-driven units.
2. Fewer bearing bores significantly reduces machining costs and more castings can be machined per set-up due to smaller size.
3. Marginal contact with cover sheet allows good heat transfer to the entire area of the casting thus promoting motor cooling.
4. Provides unique integration of gear housing and brake mechanism casting, thus eliminating one casting and providing closer alignment of bores without costly dowel pinning required in two-part assemblies.
5. Contains extended brake mechanism bore for inexpensive efficient oil return path to reservoir, by way of intermediate gear which in turn lubricates main bull gear. The intermediate gear also slings oil in all directions for heat transfer to all heat sink areas of mechanism.
Features of improved gearing:
1. Extremely compact gear train with highest gear ratio produced by only two gears and two pinions.
2. Intermediate umbrella gear serves as medium torque drive gear, bearing mount, oil slinger, oil pumper and circulator for lubricating and cooling purposes.
The high speed pinion and its shaft forms a low torque high speed drive means, and constitutes a mounting means for bearings, brake mechanism, motor and clutch.
Other detailed features and advantages of the invention while not specifically mentioned here will become apparent during the course of the following detailed description.